The present invention relates to a method and an apparatus for sorting mails by destination address and rearranging them in sequence sorting.
The mail processing is roughly divided into the dispatch sorting work and the delivery sorting work. The dispatch sorting work is the one in which mails received are sorted by the destination area in the post office. The delivery sorting work, on the other hand, is the one in which mails for delivery are sorted by the territory of each postman and rearranged by the postman in the sequence sorting in the particular territory.
A most portion of sequence sorting has conventionally been performed manually and represents a large proportion of the postmen's work time. Demand is now high for improving the efficiency of the delivery sorting work, i.e., for mechanization and automation of the entire delivery sorting work including sequence sorting.
With the aim of eliminating the conventional manual work, an information mechanization plan is going on for improving the mail process by introducing a new postal code (ZIP code) system. Specifically, address described on mails are read and corresponding address codes are printed on the mails. For delivery sorting and sequence sorting, the sorter reads the address code printed on each mail and thus automatically sorts the mails. As a result, more detailed sorting by machine than the current sorting system becomes possible for delivery. In this way, all the sorting work for delivery including sequence sorting can be mechanized theoretically.
The prior art related to the above-mentioned techniques are disclosed in JP-B2-3-18952 and JP-B2-61-14878.
In the technique disclosed in JP-B2-3-18952, each of paper items (mails) carries an indication representing a plurality of high and low hierarchical sorting levels. Mails in stages of high-level sorting are sorted by a radial sorting system, and mails in stages of low-level sorting are sorted by a rearrangement sorting system. Consequently, the mails are sorted a lesser number of times, and even in the case where the sorter goes out of order during the sorting operation, the result of sorting already completed remains unaffected and can be effectively utilized to continue subsequent sorting work.
The system disclosed in JP-B2-61-14878, on the other hand, concerns the technique in which mails are sorted according to an indication carried thereon representing a plurality of coarse and fine sorting levels. In the coarse sorting, the number of all the mails processed is stored by destination area in a memory. On the basis of this information, the mails addressed to given areas, which have been processed and are fewer than a predetermined number, are stacked in the same deposit section in the fine sorting stage. As a result, the number of mails in each deposit section can be averaged out thereby facilitating the mailing work.
As described with reference to the prior art above, several methods are available for rearranging data using the computer. Generally, however, the cardinal number sorting method is well known. The cardinal number sorting method accomplished in two levels will be described below. In this method, mails are rearranged by number based on the same principle as the conventional rearrangement sorting system.
Assume that mails carrying two-digit numbers are rearranged by the number. In the first pass, mails are sorted by the first-order digit. In other words, mails having the same least-significant digit are singled out. In the second pass, the mails rearranged in the first pass are applied in that order through the sorter. The mails are thus sorted and rearranged by the second-order digit of the number. In this way, all the mails to be sorted can be arranged according to the two-digit numbers.
In the cardinal number sorting method described above in which mails are rearranged in two sorting passes, however, some mails sorted in the second pass may overflow. In other words, mails may be stacked in some bin or stacker beyond their capacity. In such a case, extra mails that have overflown are stacked in a collective deposit section. These extra mails are disrupted in order, thereby making the first-pass sorting useless.